1. Field of the Invention
The present invention generally relates to a laminated structure including functional layers such as a conductive layer and an insulating layer, a method of producing the laminated structure, a multilayer circuit board, an active matrix substrate, and an electronic display.
2. Description of the Related Art
Printing methods are popularly used for forming patterns of functional materials (such as conductive materials, insulators, and semiconductors) that are used, for example, in electronic circuits. In a typical printing method, a pattern is formed by depositing a predetermined amount of a functional fluid containing a functional material on specified areas of a substrate (see, for example, patent documents 1 and 2).
Although photolithography enables formation of very fine functional material patterns, printing methods have advantages over photolithography in terms of equipment costs, the number of pattern forming steps, and material-use efficiency. However, with conventional printing methods, deposited functional fluid tends to spread on the substrate or to agglomerate and form a mass. This problem in turn makes it difficult to form a fine functional material pattern.
Patent documents 1 and 2 disclose a method to solve the above problem. In the disclosed method, a wettability-variable layer containing a wettability-variable material, whose surface energy changes when energy is applied, is formed on a substrate. Next, energy such as ultraviolet light is applied to a portion of the wettability-variable layer. As a result, two areas having different surface energies are formed on the wettability-variable layer. Then, a functional fluid is deposited selectively on one of the two areas (high-surface-energy area) having a surface energy higher than that of the other one of the two areas (low-surface-energy area).
Patent document 3 discloses a method to prevent the spread of a functional fluid on a substrate. In the disclosed method, banks are formed on a substrate and a functional fluid is poured into a groove between the banks.
Also, in this method, before depositing a functional fluid, a high-surface-energy area is formed on the groove between the banks and low-surface-energy areas are formed on the banks. The difference in surface energy enables the functional fluid to smoothly flow into the groove and thereby makes it possible to form a fine and uniform functional material pattern.
[Patent document 1] Japanese Patent Application Publication No. 2005-310962
[Patent document 2] Japanese Patent Application Publication No. 2006-278534
[Patent document 3] Japanese Patent Application Publication No. 2005-12181
FIGS. 1A through 2G are drawings used to describe problems in the above conventional methods for forming functional material patterns.
With the conventional method disclosed in patent documents 1 and 2, as shown in FIG. 1A, if the diameter of a drop of a functional fluid 1 deposited on a high-surface-energy area 2a is larger than the width of the high-surface-energy area 2a, the functional fluid 1 may overflow into a low-surface energy area 2b. 
A typical diameter of a functional fluid drop jetted by an inkjet method is several tens of μm or larger. As shown in FIG. 1B, taking into account a positional deviation L of a drop of the functional fluid 1 jetted by a nozzle 3 and the accuracy of positioning by a stage (not shown) holding a wettability-variable layer 2, it is obvious that forming a functional material pattern having a width of less than several tens of μm is difficult with the conventional method disclosed in patent documents 1 and 2.
For example, with the conventional method disclosed in patent documents 1 and 2, it is difficult to form fine conductive patterns (or wiring) constituting transistors of an active matrix substrate. In other words, using the above conventional method for forming transistors of an active matrix substrate may degrade the quality of the transistors and consequently degrade the performance of an electronic display including the active matrix substrate.
As described above, the method disclosed in patent document 3 makes it possible to form a fine and uniform functional material pattern. However, formation of banks for forming a fine groove having a width equal to or smaller than several tens of μm is difficult with a printing method. Therefore, it is necessary to use a photolithography process including many steps to form such fine banks. For example, a photolithography process for forming banks involves the following steps (a) through (g) shown in FIGS. 2A through 2G:                (a) A bank material is applied to the upper surface of a substrate 11 to form a bank layer 12 (bank layer forming step).        (b) A resist material is applied to the upper surface of the bank layer 12 to form a resist layer 13 (resist layer forming step).        (c) A portion of the resist layer 13 is exposed to ultraviolet light 15 through a photomask 14 (exposure step).        (d) The exposed portion of the resist layer 13 is removed by using an alkaline solution (development step).        (e) A portion of the bank layer 12 corresponding to the removed portion of the resist layer 13 is removed by etching (etching step).        (f) Remaining portions 13A of the resist layer 13 are removed and a high-surface-energy area 16 is formed on the exposed surface of the substrate 11 by O2 plasma-treatment (high-surface-energy area forming step).        (g) Then, low-surface energy areas 17 are formed on remaining portions 12A of the bank layer 12 by CF4 plasma-treatment (low-surface-energy area forming step).        